Issue is present on both Unity 2018.3.6f1 & Unity 2018.3.11f1 (latest) however I can only seem to reproduce this on my laptop, as everything works fine on my PC.
I have tried both internal and external webcams but the issue is still the same. The steps I took were switching platform to android, removing the Main Camera, adding in the WikitudeCamera, changing he webcam to my external webcam and finally playing live preview.
As mentioned earlier, Unity decided to not fix this issue:
At the moment, the only workaround is to set the display scaling in Windows to 100%
guys i have a wikitude version which orks fine with unity
I meet the same problem just now. But luckily, when I delete the default Main Camera provided by Unity, Wikitude Camera starts to display on Game Panel.